package org.zjframework.traceframe.common.util.rsa;

public class Base64
{
  private static char[] Base64Code = {
    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
    'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
    'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
   'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
    'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
    'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
    '8', '9', '+', '/' };

  private static byte[] Base64Decode = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, 62, -1, 63, -1, 63, 52, 53,
    54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
    -1, 0, -1, -1, -1, 0, 1, 2, 3, 4,
    5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
    15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
    25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
    29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
    39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
    49, 50, 51, -1, -1, -1, -1, -1 };

   public static String encode(byte[] b)
   {
    int code = 0;
    if (b == null)
      return null;
    StringBuffer sb = new StringBuffer((b.length - 1) / 3 << 6);
    for (int i = 0; i < b.length; i++)
     {
      code |= b[i] << 16 - i % 3 * 8 & 255 << 16 - i % 3 * 8;
      if ((i % 3 != 2) && (i != b.length - 1))
         continue;
      sb.append(Base64Code[((code & 0xFC0000) >>> 18)]);
      sb.append(Base64Code[((code & 0x3F000) >>> 12)]);
      sb.append(Base64Code[((code & 0xFC0) >>> 6)]);
      sb.append(Base64Code[(code & 0x3F)]);
      code = 0;
     }

    if (b.length % 3 > 0)
      sb.setCharAt(sb.length() - 1, '=');
    if (b.length % 3 == 1)
      sb.setCharAt(sb.length() - 2, '=');
    return sb.toString();
   }

   public static byte[] decode(String code)
   {
    if (code == null)
      return null;
    int len = code.length();
    if (len % 4 != 0)
      throw new IllegalArgumentException("Base64 string length must be 4*n");
    if (code.length() == 0)
      return new byte[0];
    int pad = 0;
    if (code.charAt(len - 1) == '=')
      pad++;
    if (code.charAt(len - 2) == '=')
      pad++;
    int retLen = len / 4 * 3 - pad;
    byte[] ret = new byte[retLen];
    for (int i = 0; i < len; i += 4)
     {
      int j = i / 4 * 3;
      char ch1 = code.charAt(i);
      char ch2 = code.charAt(i + 1);
      char ch3 = code.charAt(i + 2);
      char ch4 = code.charAt(i + 3);
       int tmp = Base64Decode[ch1] << 18 | Base64Decode[ch2] << 12 | Base64Decode[ch3] << 6 | Base64Decode[ch4];
      ret[j] = (byte)((tmp & 0xFF0000) >> 16);
      if (i < len - 4)
       {
        ret[(j + 1)] = (byte)((tmp & 0xFF00) >> 8);
        ret[(j + 2)] = (byte)(tmp & 0xFF);
       }
       else {
        if (j + 1 < retLen)
          ret[(j + 1)] = (byte)((tmp & 0xFF00) >> 8);
        if (j + 2 < retLen)
          ret[(j + 2)] = (byte)(tmp & 0xFF);
       }
     }
    return ret;
   }
}